Nail feeding mechanism for pneumatically operable impact tools



Nov. 21, 1967 NAIL FEEDING MECHANISM FOR PNEUMATICALLY OPERABLE IMPACT TOOLS Filed Dec. 27, 1965 F. C.HbWARD ETAL I 3,353,737

3 Sheets-Sheet 1 Fig! E FRANK c. HOWARD ARTHUR LANG/1.5

By Q- Nov. 21, 1967 F. c. HOWARD ETAL 3,353,737

OPERABLE IMPACT TOOLS HAIL FEEDING MECHANISM FOR PNEUMATICALLY Fi led Dec.

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NAIL FEEDING MECHANISM FOR PNEUMATICALLY OPERABLE IMPACT TOOLS Filed 3 Sheets-Sheet 5 Ell , A92 446 L80 X I36 6 /70' 202 I (1| v V I 1 L I68 7 Q INVENTORS I67 S FRANK c. HOWARD /44 S ARTHUR LA/VGAS United States Patent ABSTRACT OF THE DISCLGSURE A pneumatically operated gun-type nailer for driving ribbon-connected nails having enlarged heads and depending shanks. A novel feeding mechanism includes a trip latch which is axially reciprocable to feed the nails, one at a time toward a driver slot from which they are driven into the work by a piston-actuated driver. A small plunger is projected from a cylinder each time the driver substantially completes its power stroke and retracts the trip latch for a subsequent power stroke under the influence of a spring. The trip latch, in its advanced position, underlies the enlarged head of the nail in the driver slot. As the nail is ejected, the nail head engages the trip latch and defiects it laterally.

The improved nail feeding mechanism of the present invention has been designed for use primarily in connection with portable pneumatically operable nailing tools of the type employing a pneumatically operable piston and cylinder assembly for powering the driver ordinarily associated with such tools, a nose piece presenting a driver slot in alignment with the driver, a magazine for storing nails and affording a nail track along which the nails are successively fed to the driver slot, a valve for controlling the admission of air to and the exhaust of air from the cylinder to actuate the piston, and a trigger for manipulating the valve.

Impact tools of the character briefly outlined above are commonly employed for driving staples as well as nails, a slight modification being required in the shape of the driver and the driver slot so that they will accommodate the shape of the crown portions of the staples, and further modification for the same reason being required in the magazine and in the staple track leading to the driver slot in the nosepiece. Otherwise the essential features of either a pneumatic nailing tool or a pneumatic stapling tool remain substantially the same.

However, the problems which arise in connection with the feeding of nails from a magazine into driving position in a nailing tool are widely different from those which arise in connection with the feeding of staples. invariably staples are contiguously coherent so that a stick of such staples may yieldingly be urged endwise toward the driver slot by means of a suitable spring pressed follower and the staples may be struck by the driver from the leading edge of the stick until all of the staples have been consumed. Where nails are concerned, due to the enlarged heads associated therewith, the nails cannot conveniently be contiguously cohered and this has necessitated the wiring, tieing, taping or otherwise causing the nails to be interconnected so as to provide a flexible nail strip wherein adjacent nail shanks are spaced from each other by a distance at least equal to the diameter of a nail head. The strip, being flexible, does not lend itself to convenient feeding inasmuch as it is incapable of being pushed and Patented Nov. 21, 1%67 must therefore be pulled. To pull such a nail strip, various forms of cogwheel feeders have been provided but these require a complicated drive train for actuating the cogwheel, and depend on manual pressure for their operation. Furthermore, space limitations require the actual nail-engaging cogwheel to be positioned in advance of the driver slot a'distanceequal to two or more nail spacings so that the leading nail is only loosely forced into the driver slot and is loosely positioned in the slot at the time the driver descends thereon. Additionally, the character of the cogwheel employed must be a function of the nail spacing in any given nail strip. Because manual pressure is required for actuating these cogwheel type feeding devices, not only is manual skill required in the operation of the tool, but care must be taken to exert such manual pressure each time a nail is to be driven. In the absence of proper manipulation of the feeding device, the driver will descend on an empty driver slot.

Efforts to produce a more reliable nail feeding mechanism than is possible in connection with cogwheel type mechanisms have resulted in the development of nail strips which are relatively rigid, so that they may be impelled by the pushing action of a spring. This has been accomplished by close spacing of the nail heads and the use of a tightly twisted wire connector or, alternatively, by the use of two adhesive tape strips, one on each side of the row of nails, together with an intervening mass of hardened glue or other adhesive. Not only is the production of such a nail strip costly from the standpoint of assembly mechanism and materials involved, but the number of nails which can be loaded into a magazine of reasonable size is extremely limited when it is considered that with the larger size nails only four or five nails to the inch are possible. This necessitates frequent magazine loading operations.

The present invention is designed to overcome the above-noted limitations that are attendant upon the construction and use of conventional nail feeding mechanisms for impact tools and, toward this end, the invention contemplates the provision of a novel nail feeding mechanism which is effective to feed a continuous flexible nail strip by withdrawing the same from a magazine by a pulling action and which, moreover, is effective on the leading nail in the series to positively engage the same and forcibly project the nail into the driver slot and fixedly hold the same within the slot against dislodgement until such time as the driver descends upon the nail and dislodges the same for nail driving purposes. The invention further contemplates the provision of a nail feeding mechanism which, instead of depending upon manual pressure for its operation, utilizes the air pressure which is provided for piston operation and which therefore becomes automatically effective each time the trigger is actuated to drive a pre-positioncd nail from the driver slot and at the same time feed a new nail into position within the slot for the next succeeding nail driving operation. To accomplish these aims, the present nail feeding mechanism employs a novel reciprocable nail-engaging trip latch which is movable between an advanced position wherein it closes one side of the driver slot so as to positively confine a nail within the slot against lateral displacement and thus insure proper alignment of the nail with the driver, and a retracted position wherein it engages the leading nail in the series of nails issuing from the magazine for nail impelling purposes. In moving from its advanced position to its retracted position, the latch trips over such leading nail and moves to a position behind the nail so that in moving to its advanced position during the return stroke thereof the nail will be impelled into the driver slot, while at the same time the nail strip will be indexed by one nail spacing. Due to the fact that the latch, when in its advanced position, engages or directly opposes the nail shank of a nail within the driver slot, it therefore underlies the enlarged nail head. In order that the thus positioned latch shall not interfere with driving of the nail from the driver slot, means are provided whereby the latch will automatically become displaced upon contact by the nail head in passing, the latch moving to one side to allow the nail head to pass and the driver to descend fully into the driver slot. Immediately thereafter the latch is moved under the influence of air pressure to its retracted position to pick up the next nail in the series and the driver returns to its elevated position.

The provision of a nail feeding mechanism such as has briefly been outlined above and possessing the stated advantages constitutes the principal and general object of the present invention. It is a further and more specific object to provide such a nail feeding mechanism employing a reciprocable nail-engaging latch member having novel means associated therewith for yieldingly biasing the same to its normal nail-engaging position in operative register with the nail strip undergoing feeding, and also for yieldingly biasing the latch member toward its advanced nail-retaining position, the biasing function in both instances being eifected under the control of a common biasing spring.

Another object of the present .invention, in an impact tool of the character under consideration, is to provide a reciprocable latch mechanism which automatically becomes effective for nail indexing purposes each time the actuating trigger of the tool is manipulated, which continues to operate automatically until the last nail in the series has been deposited in th edriver slot, and which also has means associated therewith whereby the same may be manually operated to facilitate initial loading of the tool, to relieve a possible condition of nail jam in the vicinity of the driver slot, or for any other reason whatsoever.

A still further and important object of the invention is to provide a novel pneumatic control system for actuating the reciprocable latch mechanism, the control system being dependent for its operation upon the admission of live air to a small plunger and cylinder arrangement at such time as the driver-actuating piston is in its advanced or down position and the driver consequently is at the bottom of its stroke, By such an arrangement, the latch member is maintained in its effective nail-guiding position in the vicinity of the driver slot until such time as the nail therein has been completely expelled from the slot, after which the latch member may then move to its retracted position to pick up the next succeeding nail to be impelled to the driver slot. In carrying out this last mentioned object, means are provided whereby a small amount of live air is bled through the wall of the driver-actuating piston at such time as pressure is maintained in the upper end of the associated cylinder. The amount of air thus bled through the piston wall is insuficient to appreciably affect the power stroke of the piston and, during the down stroke of the piston the thus bled air is exhausted to atmosphere with the residual air in the lower end of the cylinder. However, at such time as the piston reaches the bottom of its stroke, the lower open rim thereof is caused to seat upon the adjacent end wall of the cylinder, thus establishing an internal pressure chamber within the confines of the piston. A bleeder passage extends from this internal pressure chamber through the adjacent end wall of the cylinder and is in effective communication with the small cylinder which houses the latch-actuating plunger. Thus, at such time as the piston reaches the bottom of its stroke, live air is conducted to the small cylinder and plunger arrangement for latch-actuating purposes and,

as soon as the piston commences its upward or return stroke, the air seal which establishes the pressure chamber is broken and the latch mechanism is returned by spring pressure to its advanced or normal position. The latch control system of the present invention therefore is completely devoid of movable control devices such as extraneous valve mechanisms, pressure-sensitive devices and the like. A simple porting arrangement leading from the usual pressure chamber above the driver-actuating piston to the plunger and cylinder arrangement which actuates the latch mechanism, through the piston wall and through the cylinder end wall, is therefore effective under the control of the conventional trigger-actuated valve mechanism of the impact tool to cause automatic actuation of the present nail feeding mechanism with no consideration on the part of the operator other than to depress the trigger for nail driving purposes being required.

The provision of a nail feeding mechanism which is extremely simple in its constructou; one which is comprised of a minimum number of parts, particularly moving parts, and which therefore is unlikely to get out of order; one which is rugged and durable and which therefore will withstand rough usage; one which, when embodied in an impact tool, is readily accessible for manual operation during tool loading operations and for inspection in the case of trouble; one which is capable of ease of assembly and disassembly for purposes of inspection of parts, replacement or repair; one which is of a compact nature and therefore consumes but little space so that the overall dimensions of the impact tool to which it is applied may be kept within reasonable limits; and one which, otherwise, is well adapted to perform the services required of it, are further desirable features which have been borne in mind in the production and development of the present invention.

Other objects and advantages of the invention, not at this time enumerated, will become readily apparent as the nature of the invention is better understood,

In the accompanying three sheets of drawings forming a part of this specification, one illustrative embodiment of the invention has been shown.

In these drawings:

FIG. 1 is a fragmentary sectional view taken substantially centrally and longitudinally through a pneumatic impact tool embodying the nail feeding mechanism of the present invention, certain parts being shown in elevation in the interests of clarity.

FIG. 2 is a fragmentary exploded perspective view showing the main body or nosepiece casting of the tool and illustrating the relationship it bears to the various elements of the nail feeding mechanism;

FIG. 3 is a sectional view taken substantially along the line 33 of FIG. 1;

FIG. 3a is an enlarged sectional view taken on the line 3a3a of FIG. 3;

FIG. 4 is a sectional view, partly in elevation, taken substantially along the line 4-4 of FIG. 1 and showing the nail feeding mechanism in its normal position;

FIG. 5 is a sectional view similar to FIG. 4, illustrating the manner in which the nail-engaging and feeding latch element proper is angularly displaced from its normal horizontal plane during the nail-driving operation;

FIG. 6 is a sectional view similar to FIG. 4, and illustrating the manner in which the latch element is angularly displaced within its normal horizontal plane during movement thereof to its retracted position; and

FIG. 7 is a sectional view similar to FiG. 4, illustrating the latch element in its fully retracted position preparatory to performance of its nail-indexing operation on the return stroke thereof.

Referring now to the drawings in detail and in particular to FIGS. 1 and 2, the nail feeding mechanism of the present invention has been designated in its entirety at 10 and, for exemplary purposes, it is shown as being embodied in a portable, gun-type percussion or impact tool in the form of an air-operated, magazine fed, nailing tool 11. The tool 11 involves in its general organization a composite tool casing 12 having upper and lower inturned flanges 14 and 16 within which there is press fitted or otherwise secured a piston and cylinder assembly 18 including a cylinder 20 and a piston 22 axially reciprocable therein. Preferably, but not necessarily, the piston and cylinder assembly 18 is of the type shown and described in United States patent to Arthur Langas, No. 3,229,589, granted on J anu ary 18, 1966, and entitled Impact Tool and Pneumatic Piston Return System Therefor. Reference may be had to such patent for a full understanding of the nature and operation of such a piston and cylinder assembly and it is deemed suflicient to state herein that the cylinder 20 presents an internal tapered or frusto-conical working surface 24 of small slant angle, while the piston 22 is re cessed as at 26 so that, in combination with the tapered working surface 24, it establishes an air pocket 28 which travels with the piston. When live air is admitted to the large end of the cylinder to drive the piston downwardly, some of this air is bled through a small passage 30, past a check valve 32 and enters the air pocket 28, thus becom ing entrapped in the latter. When air in the upper large end of the cylinder is relieved, the piston floats back to its uppermost position under the influence of the air which has become entrapped in the air pocket 28, all in a manner clearly described in the above-mentioned patent to Langus.

The piston 22 is guided in its movements by means of a plunger 40, the upper end of which is fixedly secured to the piston and the lower end of which projects outwardly of the cylinder through a bore 4-2 formed in a lower end wall 44 which substantially closes the lower end of the cylinder 20 except in the provision of a bleeder port 45 therein. The end wall 44 constitutes part of a nosepiece casting 46 which is suitably secured to the casing 12 (see also FIG. 3) and which is provided with a nosepiece proper 48 having a vertically disposed driver slot 50 therein. The driver slot 50 is in vertical register with the bore 42 in the end wall 44 as is customary in connection with portable nailing tools of the character under consideration and the plunger 40 constitutes a driver by means of which a series of nails, such as those indicated at N in FIG. 1, issuing from a magazine 52, and which are successively fed to the driver slot 50 by the nail feeding mechanism of the present invention, may be expelled from the slot and forcibly driven into the work.

The upper end of the tapered cylinder is closed b means of a hollow closure cap 60 having a lower wall 62 which projects across the otherwise open upper end of the cylinder. A gasket 64 is interposed between the wall 62 and casing 12 in sealing relationship. A lateral extension 66 constitutes a handle for the casing and is adapted to be connected by a suitable nipple fitting 68 to a flexible conduit 70 leading to a source of air under pressure (not shown).

The wall 62 overhangs the upper rim of the cylinder 20 and this overhanging portion divides the interior of the casing 12 into an upper chamber 72 and a lower chamber 74. The chamber 72 communicates with the upper end of the cylinder 20 through a port 76. The two chambers '72 and 74 communicate with each other through a port 78.

An elongated spool valve 80 projects through the port 78 and has an enlarged lower end 82 guided in a socket 84 provided internally in the handle portion 66 and sealed to the wall of the socket by an O-ring 86'. The upper end of the spool valve 80 is provided with an enlargement 88 which is guided in a socket 90 provided internally in the closure cap 60. The medial region of the spool valve 80 is formed with a third enlargement 92 which constitutes a closure valve for the port 78.

The socket 84 normally communicates through an air passage94 with the chamber 74 and a ball check valve 96 is adapted, upon actuation of a pivoted trigger element 98, to be forced against a downwardly facing seat 100 and pre 6 vent communication between the socket 84 and chamber 74. The ball 96 normally rests upon an upwardly facing seat 102 associated with a passage 104 leading to the atmosphere. A thrust pin 106 of cruciform configuration is slidable in the passage 104 and operates to displace the ball 96 when the trigger element is depressed.

The socket communicates through a passage 108 with the atmosphere and through a port 110 with the chamber 72. An O-ring 112 encompasses the port 110 and is designed for sealing engagement with the enlargement 88 when the spool valve 80 is in its lowermost position. When the spool valve 80 is in its uppermost position, the chamber 72 is bled to atmosphere through the port 110 and passage 168.

Without regard to the nail feeding mechanism 10 of the present invention and which will be described in detail subsequently, in the operation of the impact tool 11, the spool valve 80 will normally be maintained in its uppermost position since air pressure within the chamber 7 4 will be effective through the passage 94 to maintain full work ing pressure on the underneath side of the enlargement 82, as well as to maintain pressure upon the closure valve 92. The closure valve will therefore close the port 78 while the enlargement 88 will be raised from the port 110 so that pressure in the upper end of the cylinder 20 will be bled to the atmosphere through the port 110 and passage 103. The pressure of residual entrapped air within the pressure chamber 28 will thus maintain the piston 22 in its fully raised or retracted position due to considerations previously set forth. I

Upon depression of the trigger element 98, the ball 96 will become dislodged from the valve seat 102, thus bleeding the socket 84 to the atmosphere through the passage 104. The ball 96 will engage the seat and close the passage 94 so that air at working pressure within the chamber 7 4 will act upon the enlargement 82 and cause the spool valve 80 to move downwardly, thus opening the port 78 and at the same time causing the enlargement 88 to make sealing engagement with the Oring 112 and close the port 110.

At this time, working pressure within the chamber 74 will be transmitted through the port 78 to the chamber 72, from whence it will be applied through the port 76 to the upper end of the cylinder 20, thus forcing the piston 22 downwardly while at the same time forcing air through the passage 30 in the piston 22 past the check valve 32 and filling the pressure chamber 28. Upon release of the trigger element 98, the ball 96 will return to its seat 102, thus returning the spool valve 80 to its uppermost position and bleeding the upper end of the cylinder 20 to the atmosphere through the port and passage 108, whereupon the piston 22 will perform its return stroke under the influence of expansion of air within the pressure chamber 28 in the manner previously described.

The arrangement of parts thus far described are, in the main, conventional and no claim is made herein to any novelty associated with the same. As previously stated, the piston and cylinder assembly 18 with its pneumatic-ally operable piston return system constitutes the subject matter of the above mentioned patent to Langas, while the control system for actuating such assembly under the control of the trigger element 98 constitutes an incidental disclosure of such patent. The invention of the present application consists rather of the novel nail feeding mechanism 10 by means of which the nails N are conducted from the magazine 52 to the driver slot 50 and which will now be more fully described and subsequently claimed.

Referring now to FIG. 1, the nails N undergoing feeding preferably, but not necessarily, are in the form of a coherent flexible nail strip of the type shown and described in our copending United States patent application, Ser. No. 499,476, filed Oct. 11, 1965, and entitled Nail Cartridge for Driving Tool Magazines and Flexible Nail Strip Therefor. These nails may be enclosed within a disposable cartridge capable of being loaded bodily into the magazine 52in such a manner that they may be drawn successively from the magazine and cartridge, all in a manner clearly set forth in such application. Only a portion of the magazine 52 in the vicinity of the nosepiece 48 has been disclosed herein, this portion presenting a horizontal channel 120 (FIG. 2) for guiding the shank portions 122. of the nails N in their path of travel toward the driver slot 48. The nails N have enlarged heads 124 which travel in a horizontal guide slot 126 (FIGS. 2 and 3) provided in the nosepiece casting 46 in a manner that will be made clear presently when the details of the nosepiece casting are set forth. The nails N are maintained in their cohered relationship by means of one or more webs of flexible tape 128 which are suitably adhered to the nail shanks 122 so as to provide a continuous elongated nail strip or assembly wherein adjacent nails are spaced from each other a slight distance and which is of such flexibility as to enable the strip to be loosely gathered in a compact mass within the enlarged body portion of the magazine for subsequent withdrawal endwise therefrom and passage through the channel 120 and guide slot 126 in straight line fashion toward the driver slot 50.

As best seen in FIG. 2, the nosepiece casting 46 is inclusive of the lower end wall 44 for the piston and cylinder assembly 18 and the nosepiece proper 48 is suspended from this end wall by means of an interconnecting web portion 130. A horizontally disposed extension 132 projects rearwardly from the upper region of the nosepiece 48 and affords a generally rectangular channel 134 (see also FIG. 3) which opens laterally on one side of the casting 46 and the open side of which is adapted to be closed by means of an enlongated flexible spring closure strip 136 having a laterally turned end 138 designed for slid-able reception in a pair of retaining slots 139 formed in the side walls of the channel 134. Pins 140 which extend through holes 141 provided in a pair of channel wall extensions 142 serve to maintain the closure strip in position. When the closure strip 136 is in position over the channel 134, a closed rectangular box-like structure is provided within which there is operatively disposed a three-part nail-feeding latch assembly 143 (FIG. 2) including an articulated plunger and latch unit 144, a follower 146 and a biasing spring 148. The forward end of the box-like structure is closed by means of a small cylinder 150 integral with the casting 48 and into which the forward end of the plunger and latch unit projects.

The nosepiece casting 46 further includes a vertically disposed web portion 152 having bolt holes 154 therein which register with mating bolt holes 156 in the magazine 52 to the end that the magazine may be removably secured to the nosepiece casting 46 by suitable fastening bolt and nut assemblies 158. As best seen in FIGS. 2, 3a and 3, a pair of vertically spaced detent fingers 160 nested within recesses 162 formed in the web 152 seat against saddles 164 and are yieldingly maintained in position within the recesses by means of a leaf spring 165 which is secured to the outer flat side of the web 152 by means of one of the bolt and nut assemblies 158. The detent fingers 166 project into the path of travel of the nail shanks 122 as they pass along the magazine toward the driver slot 50. The detent fingers 160 are capable of rocking movement on the saddles 164 so as to allow the nail shanks to traverse the same in the direction of nail feed and to prevent reverse movement of the nail shanks.

The plunger and latch unit 144 is reciprocable in the channel 134 along a longitudinal axis and is comprised of a generally cylindrical body or plunger proper 167 the forward end of which projects into the cylinder 150 and is sealed therein by an O-ring 168. The medial region of the plunger 167 is formed with an elongated slot 169 therein and a latch element proper 170 is pivotally mounted for limited swinging movement within the slot by means of a pin 171. As will be described in greater detail presently, the plunger and latch unit 144 is movable between the advanced position wherein it is shown in FIG. 4 and wherein a latch finger 172 on the latch element 170 en- Gil gages the foremost nail in the series of nails N and retains the same in the driver slot 50, and the fully retracted position wherein it is shown in FIG. 7 and wherein a second latch finger 174 thereon engages the penultimate nail in the series for subsequent nail-feeding purposes under the influence of the spring 148 acting through the follower 146.

Considering now the plunger and latch assembly 144 in detail, and referring to FIG. 4 wherein the assembly is illustrated in its normal position, the plunger 167 is capable not only of axial reciprocation in the channel 134 but it also is capable of limited rocking rotational movement about its longitudinal axis. The forward end of the plunger 167 is formed with a V-protuberance 176 (see also FIG. 2) which mates with a corresponding V-groove 178 provided in the follower 146. The follower 146 is generally rectangular in transverse cross section so that it is incapable of rotational movement within the channel and the forward end thereof is formed with a relatively deep pilot socket 181 therein for the spring 148.

The rear end of the spring 148 bears against the laterally turned end 138 of the closure strip 136 and thus, the compressive force of the spring is applied to the plunger 167 through the follower 146 and serves normally to main tain the plunger in its normal advanced position wherein the forward end thereof is fully projected into the cylinder 150. At the same time, the mating V-protuberance 176 and V-groove 178 are so disposed that the slot 169 extends horizontally across the channel 134 and causes the latch finger 172 to be projected into the path of travel of the series of nails N and to confine the leading nail within the driver slot 50 as clearly shown in FIG. 4.

It is to be noted that in this advanced position of the plunger 167 the latch finger 172 directly underlies the enlarged head 124 of the nail N and thus, in the absence of a provision for allowing rotation of the plunger, the latch element 170 would prevent ejection of the nail from the driver slot under the influence of the descending driver 40. Accordingly, because the plunger 167 is capable of limited rocking movement, at such time as the nail head 124 engages the latch finger 172 in passing, the latter is displaced by the nail head as illustrated in FIG. 5 so that the entire plunger and latch assembly 144 is caused to rock about the axis of the plunger to a degree sufficient to allow the nail head to pass downwardly in the driver slot 50. During such rocking movement of the assembly 144, the V-protuberance 176 exerts a camming action on the wall of the V-groove 178, thus forcing the follower rearwardly or to the right as viewed in FIG. 5, thereby compressing the spring 148 so that after the nail head has cleared the latch finger 168 the force of the spring will exert a reverse carnming action on the V-groove and V-protuberance and restore the plunger 167 to its normal position.

Reciprocation of the plunger and latch unit 144 within the channel 134 is effected under the control of live air which is periodically admitted to the cylinder each time the trigger 98 is depressed as will be described presently. When air is thus admitted to the cylinder, the plunger 167 is projected rearwardly in the channel 134 as shown in FIG. 6, and an inclined surface or edge 182 provided on the swinging latch element causes the latter to trip over the leading nail N in the series of nails and subsequently move into position behind such nail as shown in FIG. 7, while at the same time the second latch finger 174 similarly moves behind the penultimate nail in the series. Upon relief of air pressure within the cylinder 150, the spring 148 operates through the follower 146 to restore the plunger 167 to its advanced position and, during the return stroke thereof the nail strip is indexed or carried forwardly so that the leading nail N is projected into the driver slot 56 to replace the nail which has previously been driven therefrom by the driver 40.

The latch element 170 is yieldingly biased within the slot 169 to its projected position by reason of its contact with the free end of the closure strip 136 which, as shown in FIGS. 4 and 7, bears against an edge of the latch element and projects the latter into the path of movement of the nails N. However, during the tripping action of the latch element as previously described, the element swings about the axis of the pivot pin 171 as shown in FIG. 6 and displaces the free end of the closure strip 136 until such time as the latch finger 172 has passed completely over the nail N.

Normally, in the operation of the impact tool 11, the nail feeding mechanism 10 will function automatically under the influence of air admitted to the cylinder 150 each time the trigger 98 is depressed to index the nail strip and feed a nail N to the driver slot 50. Reverse movement of the nail strip at such time as the latch finger 172 trips over the leading nail N is prevented by the reaction support offered by the two detent fingers 160 which allow forward indexing of the nail strip but prevent reverse indexing thereof.

For initial nail loading purposes, and in order to index the nail strip and thus pull the first few nails in the series past the detent fingers 160 and lodge the leading nail N within the driver slot 54), means are provided whereby the nail feeding mechanism 10 may be manually indexed. Accordingly, the plunger 167 is formed with an annular groove 190 near the rear end thereof and a shift fork -192 (FIGS. 2 and 4) projects loosely into the groove 190 and has a shank portion 194 which projects outwardly of the channel 134 through a slot 196 formed in the closure strip 136. The shank portion 194 constitutes a manipulative handle by means of which the entire plunger and latch assembly 144 may be retracted and then released at will, with the same effect as that obtained when the plunger 162 is reciprocated by the admission of air to and the relief of air from the small cylinder 150. The fork 192, being loosely disposed in the groove 190, oflers no interference to rotational movement of the plunger 167 during air operation of the nail feeding mechanism in the manner previously described.

As previously stated, the nail feeding mechanism 10.is automatically operable during normal tool operation under the influence of live air which is admitted to the cylinder 150 each time the trigger element 98 is depressed. According to the present invention, no special control devices such as valves, pressure sensitive diaphragrns or the like are required for directing air to the small cylinder a simple porting system being all that is required to secure such automatic operation of the nail feeding mechanism 10. Accordingly, a small bore bleeder passage 200 (FIG. 1) is formed in the head of the piston 22 and a similar bleeder passage 202 extends through the end wall 44 and establishes communication between the interior of the cylinder and the interior of the small cylinder 150. The effective size of the bleeder passage 213i) is such that it does not appreciably afiect the power stroke of the piston 22, only a small amount of air escaping through this passage during the downstroke of the piston. No appreciable degree of pressure is developed in the lower region of the cylinder during the downstroke of the piston inasmuch as this region is bled to the atmosphere through the bleeder passage 45. However, as soon as the piston 22 has reached the bottom of its stroke, a tubular elastomeric bumper sleeve or pad 204 carried by the piston seats upon the end wall 44 as shown in dotted lines in FIG. 1, thus momentarily establishing an internal pressure chamber 2% within the confines of the piston, this pressure chamber being in direct communication with the bleeder passage 202. During the brief instant when the resilient bumper pad 204 remains seated upon the end wall 44, a relatively high degree of air pressure is created within the chamber 206, this high pressure being available by reason of the small volumetric capacity of the chamber occasioned by the provision of a tubular boss 208 which largely fills the chamber, and also by reason of a powerful and forceful compression of the resilient pad under the impacting force of the piston when the pad strikes the end wall 44. The pressure of air transmitted through the passage 2132 to the cylinder 150 is therefore adequate to insure full and effective operation of the nail feeding mechanism 10 by a complete projection of the plunger 146 to its fully retracted position within the channel 134.

It is to be noted that in the normal position of the latch mechanism as illustrated in FIG. 4, the latch finger 172 bears against the nail N within the driver slot 50 (see also FIG. 1) and causes the nail to be angularly displaced with respect to the other nails in the series and to assume an inclined position Within the driver slot by reason of the tangential relationship between the enlarged nail head 124 and the curved wall of the driver slot. It has long been recognized that a nail, so positioned within a driver slot, may more effectively be driven into the work than when the nail is coaxial with the driver slot. Where rigidly cohered nails are concerned, it has been the practice to feed the nails on a slight incline to the driver slot so that the leading nail, when it arrives in position within the slot, will assume such an inclination within the slot. This has necessitated causing the guide slot leading from the nail magazine to assume a slight inclination from the hori zontal so that all of the nails undergoing feeding are equally inclined. The present nail feeding mechanism is so designed that all of the nails undergoing feeding may assume truly vertical positions throughout their travel toward the driver slot with the leading nail in the series becoming angularly displaced as it enters the driver slot.

From the above description it is believed that the nature and many advantages of the present nail feeding mechanism will 'be apparent, whether the mechanism be applied specifically to the illustrated tool 11 or to some other form of pneumatically operable, trigger-actuated tool in which live air is admitted to the upper end of a cylinder to drive the piston downwardly and thus actuate a nail-driving impact member. In its broadest aspect, the invention is applicable to any nailing tool having a piston and cylinder arrangement for actuating a driver regardless of whether the piston is retracted under the influence of air pressure acting thereon, of spring pressure, or of a combination of air and spring pressure. Similarly, the particular illustrated pneumatic control system by means of which live air is admitted to the upper end of the cylinder to effect the power stroke thereof is not essential for operation of the present nail feeding mechanism. All that is required of an impact tool to which the nail feeding mechanism may be applied is a suitable means for conducting live air to a cylinder for piston-actuating purposes 'by manipulation of a trigger element, and control means for conducting such live air to the latch-operating plunger and cylinder immediately after the piston has delivered its power stroke. Finally, it is not essential that the pressure chamber which is established when the lower end of the piston engages the lower end wall of the cylinder be established wholly within the confines of the piston. If desired, this pressure chamber may be established in the end Wall, or partly in the piston and partly in the end wall. For an eifective application of air to the latchactuating cylinder, properly timed so that the latch assembly will go into operation at such time as a nail has been driven from the driver slot, any means whatsoever which will establish a bleeder passage from the portion of the cylinder above the piston to the cylinder 156 at the approximate time that the piston completes its power stroke will suffice. Therefore, only insofar as the invention has particularly been pointed out in the accompanying claims is the same to be limited.

Having thus described the invention what we claim as new and desire to secure by Letters Patent is:

1. In a nailing tool, in combination, a nosepiece having a vertical open-sided nail-receiving driver slot therein, a magazine establishing a guide path for conducting a series of ribbon-connected nails having enlarged heads and depending shanks successively, horizontally and sidewise in a forward longitudinal direction, to said driver slot I for subsequent ejection thereof downwardly out of the slot, and articulated latch unit reciprocable bodily along a longitudinal axis in the vicinity of said path, said unit including a body portion and a nail-engaging trip latch movable longitudinally in unison with said body portion and capable of angular turning movement about said axis between a projected angular position wherein it projects into said path for nail-feeding purposes, and a retracted angular position wherein it is withdrawn from said path, spring means yieldingly urging said trip latch to its projected position, said trip latch being engageable, iri passing, by the enlarged head of a nail in said driver slot during downward movement thereof for displacement of the trip latch to its retracted angular position against the action of said spring means said latch unit being movable between a forward advanced position and a rearward retracted position, said trip latch being operable upon repeated reciprocation of the latch unit to successively engage the shank portion of a leading nail in the series and impel the nail forwardly toward the driver slot, and means for reciprocating said latch unit.

2. In a nailing tool, the combination set forth in claim 1, wherein said means for reciprocating the latch unit comprises a cylinder carried by said nosepiece and having an open end, a plunger on the forward end of the body portion of said latch unit and projecting into the open end of said cylinder, and means for supplying motive fluid to said cylinder to drive the plunger rearwardly.

3. In a nailing tool, in combination, a nosepiece having a vertical open-sided nail-receiving driver slot therein, a magazine establishing a guide path for conducting a series of nails having enlarged heads and depending shanks successively, horizontally and sidewise in a forward longitudinal direction to said driver slot, an articulated latch unit reciprocable bodily in a longitudinal direction in the vicinity of said path between a forward advanced and a rearward retracted position, said unit including a body portion and a nail-engaging trip latch pivoted for independent movement thereon between a normally projected position wherein it extends into said path, and a retracted position wherein it is withdrawn from said path, spring means yieldingly urging the trip latch to its normally projected position, said trip latch, when in its normally projected position, extending across the open side of the driver slot and partially into the same so as to directly underlie the enlarged head of a nail within the slot when the latch unit is in its advanced position, said body portion of the latch unit being yieldingly rotatable under the influence of engagement of the trip latch by said enlarged head during endwise projection of the nail from the driver slot to deflect the trip latch laterally from its normally projected position to an angularly displaced position, yieldable biasing means for said body portion effective to restore the trip latch to its normally projected position upon release thereof by the nail head, said trip latch being operable upon repeated reciprocation of the latch unit to successively engage the shank portion of a leading nail in the series and feed the nail forwardly toward the driver slot, and means for reciprocating said latch unit.

4. In a pneumatically operable nailing tool, in combination, a main cylinder having a bottom wall, an inverted cup-shaped piston axially reciprocable in said cylinder between a retracted position and an advanced position wherein its lower rim seats upon said bottom wall, thus establishing an internal pressure chamber within the piston, a nail receiving magazine connected to said cylinder, means establishing a driver slot at the end of the magazine for receiving nails therefrom, a driver connected to said piston and in register with said driver slot for driving nails therefrom, a reciprocable trip latch effective upon reciprocation to engage a nail issuing from said magazine and impel the same toward the driver slot, a secondary cylinder supported by said main cylinder, a plunger operable within the secondary cylinder and operatively connected to the latch, there being a bleeder passage in the piston establishing communication between said one end of the main cylinder and said internal pressure chamber, and a second bleeder passage in said bottom wall establishing communication between the pressure chamber and said secondary cylinder whereby, when the piston is in its advanced position, air is bled from said one end of the main cylinder, through said bleeder passages to the secondary cylinder to project said plunger and actuate said trip latch.

5. In a nailing tool, the combination set forth in claim 3, wherein the means for reciprocating the latch unit includes a spring yieldingly biasing the latch unit toward its forward advanced position, and an actuator connected to the latch unit for moving the latter toward its retracted position against the action of said biasing spring.

6. In a nailing tool, the combination set forth in claim 5, wherein said biasing spring also constitutes an element of the yieldable biasing means for restoring the trip latch to its retracted position, a nail receiving magazine conthe nail head.

'7. In a nailing tool, the combination set forth in claim 5, and including, additionally, a follower interposed between said spring and the body portion of the latch unit, means preventing rotation of said follower, and cooperating detent means on said body portion and follower and constituting said yieldable biasing means for restoring the trip latch to its normal projected position upon release thereof by the nail head.

8. In a pneumatically operable nailing tool in combination a main cylinder having a side wall and upper and lower end walls, a piston axially reciprocable in the cylinder side wall between a retracted and an advanced position, valve means for selectively admitting air under working pressure to one end of the cylinder to drive the piston downwardly from its retracted position to its advanced position and for discharging air from said one end of the cylinder to permit return of the piston upwardly to its retracted position, a nail receiving magazine connected to the cylinder, means establishing a driver slot at the end of the magazine for receiving nails therefrom, a driver connected to the piston and in register with said driver slot for driving nails therefrom, a reciprocable trip latch movable toward and away from said driver slot for nail selecting and nail-impelling purposes respectively, means yieldingly biasing said trip latch toward said driver slot, a cylinder and plunger assembly operatively connected to said trip latch and effective upon application of air thereto to move the trip latch in a direction away from the driver slot against the action of said biasing means, and means including a passage in one of the cylinder walls establishing communication between the other end of said cylinder and said cylinder and plunger assembly for supplying air to the latter at such time as the piston approaches its advanced position.

9. In a pneumatically operable nailingtool, the combination set forth in claim 4 including, additionally, a cylindrical boss formed on said end wall internally of the cylinder and which projects into the internal pressure chamber when the piston is in its advanced position, thus reducing the effective volume of the pressure chamber.

10. In a nailing tool, in combination, a nosepiece having a vertical open-sided nail-receiving driver slot therein the open side of which faces rearwardly, a magazine establishing a horizontal guide path for conducting a series of interconnected spaced parallel nails having enlarged heads and depending shank portions successively horizontally and sidewise in a forward direction to said driver slot for successive entry into the slot through the open side thereof, the nails of said series being constrained to assume positions of parallelism with the nail heads extending in coplanar relationship, means for advancing said nails successively along said guide path forwardly and sidewise into the driver slot, and means effective at such time as the leading nail in the series enters the driver slot for engaging the shank portion of such nail 1,162,677 11/1915 Boden 227136 XR Boden 227136 XR Coates et a1. Laucher. Heilman et =al. Crooks 227--136 XR Boulay 227-136 XR GRANVILLE Y. CUSTER, JR., Primary Examiner. 

8. IN A PNEUMATICALLY OPERABLE NAILING TOOL IN COMBINATION A MAIN CYLINDER HAVING A SIDE WALL AND UPPER AND LOWER END WALLS, A PISTON AXIALLY RECIPROCABLE IN THE CYLINDER SIDE WALL BETWEEN A RETRACTED AND AN ADVANCED POSITION, VALVE MEANS FOR SELECTIVELY ADMITTING AIR UNDER WORKING PRESSURE TO ONE END OF THE CYLINDER TO DRIVE THE PISTON DOWNWARDLY FROM ITS RETRACTED POSITION TO ITS ADVANCED POSITION AND FOR DISCHARGING AIR FROM SAID ONE END OF THE CYLINDER TO PERMIT RETURN OF THE PISTON UPWARDLY TO ITS RETRACTED POSITION, A NAIL RECEIVING MAGAZINE CONNECTED TO THE CYLINDER, MEANS ESTABLISHING A DRIVER SLOT AT THE END OF THE MAGAZINE FOR RECEIVING NAILS THEREFROM, A DRIVER CONNECTED TO THE PISTON AND IN REGISTER WITH SAID DRIVER SLOT FOR DRIVING NAILS THEREFROM, A RECIPROCABLE TRIP LATCH MOVABLE TOWARD AND AWAY FROM SAID DRIVER SLOT FOR NAIL SELECTING AND NAIL-IMPELLING PURPOSES RESPECTIVELY, MEANS YIELDINGLY BIASING SAID TRIP LATCH TOWARD SAID DRIVER SLOT, A CYLINDER AND PLUNGER ASSEMBLY OPERATIVELY CONNECTED TO SAID TRIP LATCH AND EFFECTIVE UPON APPLICATION OF AIR THERETO TO MOVE THE TRIP LATCH IN A DIRECTION AWAY FROM THE DRIVER SLOT AGAINST THE ACTION OF SAID BIASING MEANS, AND MEANS INCLUDING A PASSAGE IN ONE OF THE CYLINDER WALLS ESTABLISHING COMMUNICATION BETWEEN THE OTHER END OF SAID CYLINDER AND SAID CYLINDER AND PLUNGER ASSEMBLY FOR SUPPLYING AIR TO THE LATTER AT SUCH TIME AS THE PISTON APPROACHES ITS ADVANCED POSITION. 